This invention relates generally to floor grinding machines and more particularly concerns vacuum shrouds for containing dust, debris and particulates generated by the grinding process.
Older known floor grinding machines fill the air with dust and debris in a matter of minutes, making extended use inefficient, uncomfortable and unhealthy. More modern floor grinding machines use vacuum systems in an effort to reduce the dispersion of pollutants. They are ineffective because the centrifugal force at the open perimeter of the grinding wheel overcomes the vacuum suction sufficiently to quickly fill the air with dust and debris. To overcome this problem flexible shrouds have been designed so as to maintain floor contact and contain the dust and debris. However, if the machine is not flatly oriented to the floor during use, these flexible shrouds are ineffective. High volumes of dust and debris are still dispersed during the intervals in which the machine is tilted enough to expose a gap to the outer environment. These flexible shrouds are also quickly destroyed should they flex into the path of the grinding wheel. This happens most frequently when the grinding machine is used in close proximity to a wall. When the shroud is deflected into the wheel, not only is the shroud destroyed but the wheel also cuts into and damages the wall. To avoid this problem, some machines use shrouds with a diameter much greater than the diameter of their grinding wheels, but then the grinding machine cannot be positioned close to a wall or other obstacles. Also, the large diameter shroud blocks the operator""s view of the grinding wheel and the work area.
A most recent machine uses a shroud designed to maintain full contact with the floor so as to maintain vacuum suction regardless of any tilting of the grinding wheel. However, since suction is achieved by a complete seal of the shroud against the floor, the machine is pulled against the floor. This makes the machine difficult to maneuver. If the machine is tilted while suction is maintained, the angle of the grinding wheel and the force of suction cause the machine to skip out of control. If the seal is broken at all, perhaps as a result of the runaway motion of the machine or the force applied by the operator to maintain control or because of a high spot or irregularity on the floor surface, the air is filled with dust and debris as quickly as with older machines. In addition, since the shroud extends to the floor, the operator cannot see the grinding wheel or the work area. It is, therefore, difficult to properly position the machine on the floor, especially in tight areas such as next to walls and in corners without damaging the shroud and then the wall. Furthermore, the complex structure of this shroud makes it very expensive and difficult to replace.
It is, therefore, an object of this invention to provide a floor grinding machine vacuum shroud which does not contact the floor. Another object of this invention is to provide a floor grinding machine vacuum shroud which does not require a seal with the floor. A further object of this invention is to provide a floor grinding machine vacuum shroud which does not have a diameter significantly greater than the diameter of the grinding wheel. Yet another object of this invention is to provide a floor grinding machine vacuum shroud which does not cause the machine to suck against the floor. It is also an object of this invention to provide a floor grinding machine vacuum shroud which does not flex into the path of the grinding wheel. Still another object of this invention is to provide a floor grinding machine vacuum shroud which does not cause a tilted machine to run away. An additional object of this invention is to provide a floor grinding machine vacuum shroud which creates a flow of air around the periphery of the grinding wheel to control the dust and debris within the shroud. Another object of this invention is to provide a floor grinding machine vacuum shroud which permits the machine to be operated very close to walls and other obstacles. A further object of this invention is to provide a floor grinding machine vacuum shroud which is easily replaced in comparison to known shrouds. Yet another object of this invention is to provide a floor grinding machine vacuum shroud which is inexpensive in comparison to known shrouds.
In accordance with the invention, a vacuum shroud is provided for covering a grinding wheel mounted on the drive shaft of a floor grinding machine. A rigid cover has a central opening in its top through which the machine drive shaft is extended to the grinding wheel. A cylindrical skirt on the cover has a diameter preferably equal to but not less than the diameter of the grinding wheel. The skirt is concentrically disposed above the grinding wheel. A vacuum port extends through the cover. A flexible and resilient cylindrical guard has a plurality of vertical ribs inwardly protruding from its upper portion. The ribs abut the lower outer periphery of the skirt and the lower portion of the guard extends downwardly to its bottom rim which lies in a plane slightly above the plane of the grinding surface of the grinding wheel. The ribs and skirt define a plurality of vertical air inlet passages which communicate from outside of the cover to the vacuum port. The guard bottom rim is cooperable with the floor to define an annular air inlet passage around the periphery of the grinding wheel which communicate from outside of the guard to the vacuum port. A mechanism is provided for securing the ribs in abutment with the skirt, preferably a strap with an adjustable buckle for reducing the length of the strap to clamp the ribs against the skirt. Most preferably, the strap is disposed within the upper portion of the guard, perhaps by molding the strap into the upper portion of the guard. The ribs must extend at least to the bottom of the lower outer periphery of the skirt and, for best results, the ribs should extend slightly below the lower outer periphery of the skirt. Preferably, the cover is made of steel and the guard is made of polyurethane.